A method of the kind mentioned in the opening paragraph is known from Netherlands patent application laid open to public inspection under No. 8702219, corresponding to U.S. Pat. No. 4,853,320. In the method described therein, a nuclei image in the form of a number of loose metal nuclei is deposited at the area of the defect during a comparatively short exposure. Subsequently, the mask is introduced into an electroless metallization solution, in which the nuclei image is intensified without further exposure. Metal is then deposited from a metallization solution selectively only on the nuclei or already deposited metal. By removing the mask from the solution, the intensification is terminated.
In the known method, however, the metal image is not fully limited to the exposed part of the mask. Due to lateral growth, at the edge of the nuclei image metal will be deposited also outside the exposed part. In order that this is limited to a minimum, the mask should be removed from the metallization solution as soon as possible after a sufficient quantity of metal has been deposited. However, the substrate must not be removed too early from the solution because the metal deposit is then not optically light-tight and the defect will not be fully restored. Especially if more defects are restored at the same time, in which event due to process tolerances one defect will inevitably be restored earlier than the other, this is disadvantageous. However, even if only one defect is restored, such an overgrowth is disadvantageous due to the fact that this results in that the resolution of the method of repairing is reduced. Especially in the modern LCD and semiconductor technology, in which masks are used with details of only a few microns or even smaller, this is disadvantageous.